1. Field of the Invention
This invention relates to an engine control system for a vehicle.
2. Description of the Prior Art
There has been proposed an electric throttle system in which the throttle valve is mechanically disconnected from the accelerator pedal and is electrically driven by an actuator such as an electric motor in response to depression of the accelerator pedal. In an accelerator control system disclosed, for instance, in Japanese Unexamined Patent Publication No. 59(1984)-122745, when the change of amount of depression of the accelerator pedal is small, a throttle control gain is reduced so that the change of the throttle opening for a given change of the accelerator depression is reduced, thereby facilitating fine control of the vehicle speed, and when the change of the accelerator depression is large, the throttle control gain is increased so that the change of the throttle opening for a given change of the accelerator depression is increased, thereby ensuring a better acceleration performance conforming to the driver's will.
However since the running state is affected by the current of traffic, if the throttle control gain is changed simply according to the amount of change of the accelerator depression, stability in control and fuel economy will deteriorate.